Denture Base Polymers

Question 1

2. According to ISO 20795-1:2013, what is the minimum flexural strength for denture base polymers?
   A. 25 MPa
   B. 45 MPa
   C. 65 MPa
   D. 85 MPa

Answer 1

C. 65 MPa

Question 2

1. What is the role of a denture base?
   A. Acts as a scaffold for bone growth
   B. Supports the prosthetic teeth and replaces lost tissue
   C. Holds the denture in place using suction
   D. Improves occlusion

Answer 2

B. Supports the prosthetic teeth and replaces lost tissue

Question 3

3. What initiates the polymerization in heat-cured PMMA?
   A. Camphorquinone
   B. Hydroquinone
   C. Benzoyl peroxide
   D. Dimethyl-p-toluidine

Answer 3

C

Question 4

4. What is the typical polymerization shrinkage of PMMA?
   A. 3%
   B. 6%
   C. 9%
   D. 12%

Answer 4

B

Question 5

5. What does the ‘glass transition temperature’ (Tg) indicate?
   A. Melting point of PMMA
   B. Temperature at which color fades
   C. Transition from rigid to rubbery state in polymers
   D. Point where porosity begins

Answer 5

C

Question 6

6. Which of these is an optical opacifier used in PMMA?
   A. Nylon
   B. Hydroquinone
   C. Titanium dioxide
   D. Dimethacrylate

Answer 6

C

Question 7

7. Which of the following is NOT a desirable property of denture base polymers?
   A. Porosity
   B. Colour stability
   C. Biocompatibility
   D. Repairability

Answer 7

a

Question 8

8. What is the function of hydroquinone in the MMA liquid?
   A. Accelerator
   B. Inhibitor
   C. Initiator
   D. Cross-linker

Answer 8

b

Question 9

9. What causes gaseous porosity in PMMA processing?
   A. Bead fusion
   B. Boiling of monomer before polymerization
   C. Lack of initiator
   D. Overuse of pigment

Answer 9

b

Question 10

10. What is a disadvantage of PMMA as a denture base?
    A. High water sorption
    B. High impact strength
    C. Poor thermal conductivity
    D. Difficult to polish

Answer 10

c

Question 11

1. Which type of porosity occurs due to premature drying of dough?
   A. Gaseous
   B. Contraction
   C. Granular
   D. Surface

Answer 11

c

Question 12

12. What is the P/L ratio used in the PMMA setting process?
    A. 1:1
    B. 2:1 by weight
    C. 1.6:1 by weight
    D. 3:1

Answer 12

b

Question 13

13. What is used as a cross-linking agent in PMMA liquid?
    A. Camphorquinone
    B. Butylene glycol dimethacrylate
    C. Titanium dioxide
    D. Hydroquinone

Answer 13

b

Question 14

14. What curing method involves tertiary amines?
    A. Heat cured
    B. Light cured
    C. Chemically cured
    D. Pressure cured

Answer 14

c

Question 15

15. What is the Tg of poly(methyl methacrylate)?
    A. 20°C
    B. 35°C
    C. 65°C
    D. 105°C

Answer 15

d

Question 16

16. What is the effect of large pendant groups on Tg?
    A. Increases Tg
    B. Decreases Tg
    C. Has no effect
    D. Depends on temperature

Answer 16

b

Question 17

17. What is the purpose of plasticizers in PMMA?
    A. Increase rigidity
    B. Enhance optical clarity
    C. Soften the resin and improve handling
    D. Prevent shrinkage

Answer 17

c

Question 18

18. Which of these is a component of the powder in heat-cured PMMA?
    A. MMA monomer
    B. Hydroquinone
    C. Benzoyl peroxide
    D. Camphorquinone

Answer 18

c

Question 19

19. What component in the liquid provides colour stability?
    A. Nylon
    B. Hydroquinone
    C. Pigment
    D. Ethyl acrylate

Answer 19

c

Question 20

20. What type of resin is used in injection moulding for dentures?
    A. Vulcanite
    B. PMMA
    C. Nylon
    D. Porcelain

Answer 20

b

Question 21

21. What is the primary disadvantage of porcelain denture teeth?
    A. Poor aesthetics
    B. Hard to polish
    C. May wear opposing teeth
    D. Prone to staining

Answer 21

c

Question 22

17. What does “resilience” refer to in polymers?
    A. Energy absorbed before permanent deformation
    B. Total deformation
    C. Fracture resistance
    D. Compressive strength

Answer 22

a

Question 23

18. What type of PMMA component increases toughness and reduces modulus?
    A. Nylon
    B. Butadiene-styrene copolymers
    C. Iron oxide
    D. Polyamide

Answer 23

b

Question 24

19. Which component helps in preventing early polymerization in MMA liquid?
    A. Titanium oxide
    B. Hydroquinone
    C. Camphorquinone
    D. Benzoyl peroxide

Answer 24

b

Question 25

20. Which of the following is a disadvantage of porcelain denture teeth? A. Low strength B. High wear on opposing teeth C. Weak bonding D. Flexibility

Answer 25

b

Question 26

21. What is the glass transition temperature of PMMA? A. 20°C B. 35°C C. 65°C D. 105°C

Answer 26

d

Question 27

22. What does the "rubbery" stage of dough formation involve? A. Partial monomer diffusion B. Bead swelling and monomer plasticization C. Full gelation D. Surface curing

Answer 27

b

Question 28

23. What accelerates chemically-cured polymerization? A. Blue light B. Tertiary amines C. UV rays D. Cross-linkers

Answer 28

b

Question 29

24. Which process step involves heating the flask in boiling water? A. Flasking B. Boiling out C. Deflasking D. Curing

Answer 29

d

Question 30

25. What does dimensional stability help prevent? A. Colour changes B. Thermal breakdown C. Warping of dentures D. Tooth fracture

Answer 30

c

Question 31

26. What is a major concern with palatine tori in upper dentures? A. Aesthetic limitations B. Risk of stress concentration C. Poor taste perception D. Thermal conductivity

Answer 31

b

Question 32

27. Which of the following makes the acrylic dough easier to handle? A. Opacifiers B. Plasticizers C. Cross-linkers D. Inhibitors

Answer 32

b

Question 33

28. Which is a historical material once used for denture bases? A. PMMA B. Vulcanite C. Nylon D. Titanium

Answer 33

b

Question 34

29. What is the function of TiO₂ in the resin? A. Initiator B. Opacifier C. Plasticizer D. Cross-linker

Answer 34

b

Question 35

30. Which stage in processing comes directly before deflasking? A. Boiling out B. Wax pattern C. Boiling D. Curing

Answer 35

d

Question 36

31. What polymer is known for poor impact strength but good polishability? A. PMMA B. Nylon C. Polycarbonate D. Polyethylene

Answer 36

a

Question 37

32. What is a disadvantage of using metal strengtheners in dentures? A. High cost B. Increased porosity C. Act as stress concentrators D. Chemical degradation

Answer 37

c

Question 38

33. What is the most common fracture site in complete upper dentures? A. Posterior border B. Midline C. Buccal flange D. Palatal vault

Answer 38

b

Question 39

34. What type of porosity typically forms deep inside the denture during polymerization? A. Granular B. Surface C. Gaseous D. Linear

Answer 39

c

Question 40

35. What feature makes polyamides (like Valplast®) aesthetically superior to PMMA? A. Metallic reinforcement B. Flexibility and translucency C. High modulus D. Cross-link density

Answer 40

b

Question 41

36. Which denture tooth material chemically bonds well with PMMA? A. Porcelain B. Nylon C. Plastic acrylic D. Fibre-reinforced ceramic

Answer 41

c

Question 42

37. What is the main benefit of high-impact acrylics like Lucitone 199? A. Increased rigidity B. Increased toughness C. Better optical opacity D. Decreased weight

Answer 42

b

Question 43

38. What happens in the ‘sandy’ stage of PMMA mixing? A. Beads begin melting B. Monomer fully penetrates the beads C. Monomer diffuses and begins softening beads D. Chain termination occurs

Answer 43

a

Question 43

39. Which of the following is a thermoplastic material used as an alternative to PMMA? A. Epoxy resin B. Polyamide C. Silicone D. Polyurethane

Answer 43

b

Question 44

40. What type of bond forms between old and new PMMA chains during processing? A. Ionic B. Covalent C. Physical entanglement D. Hydrogen

Answer 44

c

Question 45

41. Which curing method best prevents porosity and maximizes monomer conversion? A. Light curing B. Heat curing C. Cold curing D. Self-curing

Answer 45

b

Question 46

42. What is the main function of opacifiers in denture base resins? A. Increase rigidity B. Prevent shrinkage C. Improve aesthetics D. Improve thermal conductivity

Answer 46

c

Question 47

43. Which PMMA component contributes to colour vitality? A. Cross-linker B. Pigments C. Plasticizers D. Nylon fibres

Answer 47

b

Question 48

44. What describes the change in molecular structure when polymers shift from a hard to a rubbery state? A. Modulus of elasticity B. Gelation C. Glass transition D. Polymerization

Answer 48

c

Question 49

45. What is the benefit of radio-opacity in a denture base? A. Detectable on X-rays B. Resists polymer shrinkage C. Improves thermal insulation D. Enhances elasticity

Answer 49

a

Question 50

46. What processing issue occurs due to insufficient pressure during curing? A. Gaseous porosity B. Contraction porosity C. Thermal breakdown D. Monomer migration

Answer 50

b

Question 51

47. What is the role of benzoyl peroxide in PMMA formulations? A. Cross-linker B. Initiator C. Inhibitor D. Plasticizer

Answer 51

b

Question 52

48. What is the role of camphorquinone in light-cured resins? A. Pigment B. Cross-linker C. Photo-initiator D. Thermal stabilizer

Answer 52

c

Question 53

49. Which of the following additives can mimic blood vessels in a denture base? A. Nylon B. Titanium dioxide C. Coloured fibres D. Diethylene glycol

Answer 53

c

Question 54

50. Which factor lowers the glass transition temperature of a polymer? A. Increased cross-linking B. Small pendant groups C. Large pendant groups D. High crystallinity

Answer 54

c